The present invention relates to a rotary encoder that outputs three-phase rectangular wave signals, used for input operations, etc. in various kinds of electronic apparatus.
A conventional rotary encoder which outputs multi-phase rectangular wave signals is disclosed in Japanese Utility Model Laid-Open No. H3-26021, and in Japanese Patent Laid-Open Application No. H6-94476. Each of the conventional rotary encoders has a ring-shape common pattern disposed at the center of contact-point board, and a teethed ring-shape signal pattern disposed around outside of the common pattern. The signal pattern is provided for a number of phases of the output signal, disposed concentric to the common pattern. Each of the rotary encoders further has a slider, provided to be revolvable so that its movable contact points slide on the respective patterns to generate multi-phase rectangular wave signals. For example, a three-phase encoder is provided with three signal patterns. The contact-point boards used in conventional rotary encoders have large outer diameter. Therefore, the overall outer dimensions of the rotary encoder become bulky, and this makes it difficult to use the rotary encoder in a high-density compact electronic apparatus.
A rotary encoder in the present invention has a slider supported to be revolvable with respect to a contact-point board, which slider having a plurality of movable contact points disposed on a circle of a certain radius from the revolution center at an angular interval that is six times as large as the output pitch of rectangular wave signal. The rotary encoder further has, on the contact-point board, an electroconductive signal pattern and a common pattern, which make contact with the slider. The signal pattern has three fixed contact points along a sliding circle of the movable contact points. Each of the fixed contact points has two conductive layers of the same width disposed in radial arrangement having mutual electrical conduction. Angular pitch of the radial conductive layers is three times as large as the output pitch of rectangular wave signal. Angular pitch of the three fixed contact points is smaller, or larger, than the angular interval, or a multiple of it, of the movable contact points by the output pitch of rectangular wave, or twice that. Furthermore, it is larger than angular width of one of the fixed contact point. The common pattern is insulated from the signal pattern, and disposed on a sliding circle of the same radius as the movable contact points of slider. When any one of the movable contact points of the slider is making contact with any one of the fixed contact points of signal pattern, the common pattern is having contact with at least one of the rest of the movable contact points.